Refrigerant compressor

ABSTRACT

Refrigerant compressor includes an electrical drive unit, a piston/cylinder unit which can be driven by the drive unit for the cyclical compression of refrigerant, and at least one sound-damping unit made of a thermoplastic, through which sound-damping unit refrigerant can flow and which sound-damping unit includes at least one damping chamber. The at least one sound-damping unit is connected to the piston/cylinder unit in order to enable an exchange of refrigerant between the sound-damping unit and piston/cylinder unit. The at least one sound-damping unit includes at least in sections a functional surface. The functional surface is embodied such that an emissivity of a section of the sound-damping unit includes the functional surface is less than 0.7. The at least one sound-damping unit or at least one of the sound-damping units is embodied as a discharge muffler arranged downstream of the piston/cylinder unit in the direction of flow.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C. § 119(a) to EuropeApplication No. 18 198 034.3 filed Oct. 1, 2018, the disclosure of whichis expressly incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

The present invention relates to a refrigerant compressor comprising anelectrical drive unit, a piston/cylinder unit which can be driven by thedrive unit for the cyclical compression of refrigerant, and at least onesound-damping unit made of a thermoplastic, through which sound-dampingunit refrigerant can flow and which sound-damping unit comprises atleast one damping chamber, wherein the at least one sound-damping unitis connected to the piston/cylinder unit in order to enable an exchangeof refrigerant between the sound-damping unit and piston/cylinder unit.

DISCUSSION OF BACKGROUND INFORMATION

Hermetically encapsulated refrigerant compressors have been known forquite some time and are primarily used in refrigerators or refrigerateddisplay cases. The refrigerant process as such has also been known for along time. Refrigerant is thereby heated in an evaporator by anabsorption of energy from the space being cooled and is ultimatelyoverheated and pumped to a higher pressure level by the refrigerantcompressor with a piston/cylinder unit, at which pressure level it emitsheat via a condenser and is transported back into the evaporator againvia a throttle valve in which a pressure reduction and the cooling ofthe refrigerant take place.

An intake of the (gaseous) refrigerant occurs via a suction tube comingdirectly from the evaporator during an intake cycle of thepiston/cylinder unit. In known hermetically encapsulated refrigerantcompressors, the suction tube normally leads to the hermeticallyencapsulated compressor housing—usually in the vicinity of an inlet of asuction muffler, from which location the refrigerant flows into andthrough the suction muffler to an intake valve of the piston/cylinderunit. That is, as viewed in the direction of flow, the suction muffleris located upstream of the piston/cylinder unit and primarily serves tokeep the noise level of the refrigerant compressor as low as possibleduring the intake process.

Furthermore, a discharge muffler is usually located downstream of thepiston/cylinder unit as viewed in the direction of flow, which dischargemuffler serves to keep the noise level of the refrigerant compressor aslow as possible during the outflow of the compressed refrigerant.

Possibilities for improving the efficiency of the refrigerant compressorcan in particular be found in the reduction of the temperature of therefrigerant at the start of the compression process. Each reduction ofthe intake temperature of the refrigerant into the cylinder of thepiston/cylinder unit causes a decrease in the technical work necessaryfor the compression process.

In known hermetically encapsulated refrigerant compressors, a markedheating of the refrigerant takes place on the refrigerant's path throughthe suction muffler to the piston/cylinder unit for design-relatedreasons. This can be attributed to the heating of the interior of thecompressor housing, which heating primarily occurs as a result of thecompressed refrigerant discharged in the discharge muffler. Thecompressed refrigerant discharged in the discharge muffler hastemperatures of up to 180° C. and thus constitutes a significant heatsource. This leads to a heating of the interior of the compressorhousing and, as a further result, to a heat transfer to the refrigerantlocated in the suction muffler.

A heating of the interior of the compressor housing due to thecompressed refrigerant in the discharge muffler is also undesirable inregard to motor cooling.

SUMMARY

It is therefore an object of the invention to provide a refrigerantcompressor which avoids the aforementioned disadvantages. Temperatureincreases in the interior of the compressor housing are to be reduced.In particular, the refrigerant temperature at the start of thecompression process is to be kept as low as possible in order toincrease the efficiency.

With a refrigerant compressor comprising an electrical drive unit, apiston/cylinder unit which can be driven by the drive unit for thecyclical compression of refrigerant, and at least one sound-damping unitmade of a thermoplastic, through which sound-damping unit refrigerantcan flow and which sound-damping unit comprises at least one dampingchamber, wherein the at least one sound-damping unit is connected to thepiston/cylinder unit in order to enable an exchange of refrigerantbetween the sound-damping unit and piston/cylinder unit, the objectnamed at the outset is attained according to the invention in that theat least one sound-damping unit comprises at least in sections afunctional surface, wherein the functional surface is embodied such thatan emissivity of a section of the sound-damping unit comprising thefunctional surface is less than 0.7, preferably less than 0.5,particularly preferably less than 0.1.

The functional surface present at least in sections reduces the heatemission and/or heat absorption caused by radiation at the at least onesound-damping unit. Through the use of a functional surface, the atleast one sound-damping unit exhibits a reduced emissivity in thoseregions in which the functional surface is present.

The emissivity of the at least one sound-damping unit indicates how muchradiation the at least one sound-damping unit emits compared to an idealradiant heater, a black body. That is, the at least one sound-dampingunit exhibits in those regions in which the functional surface ispresent a reduced heat emission and/or heat absorption caused byradiation compared to surface sections without a functional surface. Thetemperature inside a compressor housing is thus reduced. This causes therefrigerant compressor according to the invention to exhibit a betterefficiency.

The functional surface can be embodied either on an outer surface of theat least one sound-damping unit, wherein the outer surface is facing theinterior of the compressor housing, or on an inner surface of the atleast one sound-damping unit, wherein the inner surface is facing theinterior of the at least one sound-damping unit, in particular the atleast one damping chamber.

Of course, the radiant emission and absorption are equal at a givenwavelength. That is, in addition to a reduced heat emission, thefunctional surface also leads to a reduced heat absorption.

It would be conceivable that the at least one sound-damping unit isproduced by an injection-molding method. A production method of thistype is characterized by the particular cost-efficiency thereof.

Furthermore, it would be conceivable that the functional surface ispolished in order to achieve a particularly low emissivity.

According to the invention, it is provided that the at least onesound-damping unit or at least one of the sound-damping units isembodied as a discharge muffler arranged downstream of thepiston/cylinder unit in the direction of flow.

Since the at least one discharge muffler is arranged downstream of thepiston/cylinder unit in the direction of flow, preferably inside of thecompressor housing, the functional surface must exhibit a lowemissivity. This is especially true because the refrigerant enters theat least one discharge muffler after the piston/cylinder unit with ahigh temperature due to the compression and heats the discharge muffleraccordingly. The functional surface is in this case preferably embodiedon the inner surface facing the interior of the discharge muffler andresults in an improved efficiency of the refrigerant compressoraccording to the invention, since temperature increases in the interiorof the compressor housing are reduced because the heat radiation by therefrigerant is essentially reflected back into the interior of thedischarge muffler by the functional surface.

On the discharge muffler, the functional surface can of course also beembodied on the outer surface of the discharge muffler facing theinterior of the compressor housing, and can thereby result in animproved efficiency of the refrigerant compressor according to theinvention.

It would be conceivable that additional parts of the refrigerantcompressor according to the invention are also provided with a similarfunctional surface having low emissivity, such as parts of thepiston/cylinder unit, for example.

In the refrigerant compressor according to the invention, it ispreferably provided that the thermoplastic comprises additives, forexample, aluminum and/or chromium.

In elaborate tests, it was determined that, under some circumstances, itcan be sufficient to add additives to the thermoplastic in order toachieve the formation of a functional surface with an appropriately lowemissivity and absorptivity of the at least one sound-damping unit. Thatis, in such a case, the functional surface is at least partiallyembodied by a surface section of a solid material of the at least onesound-damping unit, and no additional coating is necessary (althoughsuch a coating is also not excluded). It would also be possible that theadditives are only present in regions of the solid material of thesound-damping unit that are close to the surface.

In other words, with a refrigerant compressor comprising an electricaldrive unit, a piston/cylinder unit which can be driven by the drive unitfor the cyclical compression of refrigerant, and at least onesound-damping unit made of a thermoplastic, through which unitrefrigerant can flow and which unit comprises at least one dampingchamber, wherein the at least one sound-damping unit is connected to thepiston/cylinder unit in order to enable an exchange of refrigerantbetween the sound-damping unit and piston/cylinder unit, the objectnamed at the outset is attained according to the invention in that thethermoplastic comprises additives, such as aluminum and/or chromium, forexample, wherein the heat emission of a sound-damping unit made ofthermoplastic with additives is reduced compared to a sound-damping unitmade of thermoplastic without additives.

The heat emission and heat absorption can also be reduced if the surfaceof the solid material of the at least one sound-damping unit composed ofthermoplastic is polished.

It would be conceivable that the functional surface is only formed bythe polishing. That is, the functional surface is in this case formedeven if the thermoplastic does not comprise any additives.

Preferably, in the refrigerant compressor according to the invention, itis provided that the functional surface is embodied as a metallic layer.A metallic layer as a functional surface is characterized by a lowemission coefficient, especially if the metallic layer is polished.

However, it would also be conceivable that the functional surface isembodied as a non-metallic layer, preferably as a ceramic layer with alow emission coefficient.

In a preferred embodiment of the refrigerant compressor according to theinvention, it is provided that the at least one sound-damping unit iscompletely covered by the metallic layer. In this manner, thetemperature inside of the compressor housing is significantly reduced,since the heat absorption and heat dissipation of the at least onesound-damping unit are reduced.

A covering of the at least one sound-damping unit with the metalliclayer is particularly easy and cost-effective to produce.

Of course, the metallic layer can also be arranged on the inner surfacefacing the interior of the at least one sound-damping unit.

In a preferred embodiment of the refrigerant compressor according to theinvention, it is provided that the metallic layer contains chromiumand/or aluminum. Both chromium and aluminum exhibit, particularly with apolished surface, low emissivities and absorptivities, for which reasonthey are exceptionally well-suited to be constituents of the metalliclayer.

It would be conceivable that the layer containing chromium and/oraluminum exhibits an emissivity between 0.1 and 0.02 in a polishedstate.

It would furthermore be conceivable that the metallic layer comprisesfurther constituents in addition to chromium and/or aluminum.

In the refrigerant compressor according to the invention, it ispreferably provided that the metallic layer is embodied as a metallicfilm. The metallic layer in the form of a metallic film is characterizedby a particularly good reduction in heat emission and heat absorptionand is easy to apply.

In the refrigerant compressor according to the invention, it ispreferably provided that the at least one sound-damping unit can beobtained by back injection-molding the metallic film; that is, themetallic film is back injection-molded with the thermoplastic. In thiscase, the film is first supplied to an injection mold. Then, thethermoplastic is injected into the injection mold, wherein thethermoplastic and the film are bonded. It is advantageous that the backinjection-molding can be fully automated, and that no adhesive at all isrequired for the bonding between the thermoplastic and the film.

In a preferred embodiment of the refrigerant compressor according to theinvention, it is provided that the metallic layer is spread onto and/orpainted onto and/or glued onto and/or galvanized onto the at least onesound-damping unit. With the spreading-on and/or painting-on and/orgluing-on and/or galvanizing, the metallic layer is applied on the atleast one sound-damping unit in a simple manner. These types ofapplication are characterized by simple handling and goodcost-efficiency.

Galvanizing in particular can be easily automated, and the coatingproduced by galvanizing is characterized by low costs as well as rapidproducibility.

Preferably, in the refrigerant compressor according to the invention, itis provided that the at least one sound-damping unit or one of thesound-damping units is embodied as a suction muffler arranged upstreamof the piston/cylinder unit in the direction of flow.

Since the at least one suction muffler is arranged inside of thecompressor housing upstream of the cylinder/piston unit in the directionof flow, the functional surface must exhibit a low absorptivity. This istrue because, otherwise, the refrigerant inside of the suction mufflerwill be heated as a result of the high temperatures that are presentinside of the compressor housing—among other things due to thecompressed refrigerant discharged in the pressure tube. In this case,the functional surface is thus preferably embodied on the outer surfaceof the suction muffler facing the interior of the compressor housing andresults in an improved efficiency of the refrigerant compressoraccording to the invention, since the temperature of the refrigerantinside of the suction muffler is not increased by a higher temperatureinside of the compressor housing because the heat radiation isessentially reflected back into the compressor housing by the functionalsurface.

On the suction muffler, the functional surface can of course also beembodied on the inner surface facing the interior of the suctionmuffler, and can thereby result in an improved efficiency of therefrigerant compressor according to the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be explained in greater detail with the aid ofexemplary embodiments. The drawings are by way of example and areintended to demonstrate, but in no way restrict or exclusively describe,the inventive concept.

In this matter:

FIG. 1 shows a sectional view of a known refrigerant compressor;

FIG. 2 shows a front view of a suction muffler provided with afunctional surface;

FIG. 3 shows a sectional view of the suction muffler from FIG. 2according to the sectional line A-A drawn in FIG. 2;

FIG. 4 shows a front view of a discharge muffler provided with afunctional surface; and

FIG. 5 shows a sectional view of the discharge muffler from FIG. 4according to the sectional line B-B drawn in FIG. 4.

DETAILED DESCRIPTION

FIG. 1 shows a sectional view of a known refrigerant compressor 1. Therefrigerant compressor 1 comprises a compressor housing 8, a drive unit2, a piston/cylinder unit 3 in which the cyclical compression of arefrigerant takes place, and at least one sound-damping unit 4.

The at least one sound-damping unit 4 can be a suction muffler 6 and/ora discharge muffler 7. The suction muffler 6 is arranged upstream of thepiston/cylinder unit 3 in the direction of flow of the refrigerant,whereas the discharge muffler 7 is located downstream of thepiston/cylinder unit 3 in the direction of flow of the refrigerant.

On the path between the entry of the refrigerant into the compressorhousing 8 and the intake valve of the piston/cylinder unit 3, thereoccurs, as mentioned previously, an undesired heating of therefrigerant. This can be attributed to the heating of the interior ofthe compressor housing 8, which occurs, among other things, as a resultof the compressed refrigerant discharged in the discharge muffler 7. Thecompressed refrigerant discharged in the discharge muffler 7 therebyoccasionally has temperatures of up to 180° C. and thus constitutes asignificant heat source. This leads to a heating of the interior of thecompressor housing 8 and, as a further result, to a heat transfer to therefrigerant located in the suction muffler 6.

For this reason, both the suction muffler 6 illustrated in FIG. 2 andFIG. 3 and also the discharge muffler 7 illustrated in FIG. 4 and FIG. 5are provided with a functional surface 11 that is preferably embodied asa metallic layer 5.

FIG. 2 shows a front view of the suction muffler 6 comprising thefunctional surface 11, while FIG. 3 shows a sectional view of thesuction muffler 6 from FIG. 2 according to the sectional line A-A drawnin FIG. 2. The suction muffler 6 comprises at least one damping chamber9, but preferably multiple damping chambers 9. In FIG. 3, it can be seenthat the suction muffler 6 is completely covered with the metallic layer5.

The metallic layer 5 preferably contains aluminum and, particularlypreferably, is embodied as a film that is applied to the suction muffler6. The metallic layer 5 on the suction muffler 6 is polished in theexemplary embodiment illustrated, for which reason it has a particularlywell-reflecting surface. The metallic layer 5 thus has a lowerabsorptivity, which is why the refrigerant inside of the suction muffler6 is hardly heated, or not heated at all, as a result of the highertemperatures that can prevail in the interior of the compressor housing8.

FIG. 4 shows a front view of the discharge muffler 7 comprising thefunctional surface 11, while FIG. 5 shows a sectional view of thedischarge muffler 7 from FIG. 4 according to the sectional line 13-13drawn in FIG. 4. The discharge muffler 7 comprises at least one dampingchamber 10, but preferably multiple damping chambers 10. In FIG. 5, itcan be seen that the discharge muffler 7 is completely covered with themetallic layer 5.

The metallic layer 5 preferably contains aluminum and, particularlypreferably, is embodied as a film that is applied to the dischargemuffler 7. The metallic layer 5 on the discharge muffler 7 is polishedin the exemplary embodiment illustrated, for which reason it has aparticularly well-reflecting surface. The metallic layer 5 thus has alower emissivity, which is why the high temperature of the compressedrefrigerant is hardly transferred, or not transferred at all, to theinterior of the compressor housing 8. That is, the metallic layer 5 onthe at least one discharge muffler 7 reduces or prevents a heatemission.

Of course, additional parts of the refrigerant compressor 1 according tothe invention, such as parts of the piston/cylinder unit 3 and varioustubes, for example, can also be provided with a functional surface 11,in particular with a metallic layer 5.

Via the refrigerant compressor 1 according to the invention, temperatureincreases in the interior of the compressor housing 8 are thus reduced,whereby in particular the refrigerant temperature at the start of thecompression process, and therefore necessarily also during the intakeinto the cylinder of the piston/cylinder unit 3, is kept as low aspossible. This causes the refrigerant compressor 1 according to theinvention to exhibit a better efficiency compared to a known refrigerantcompressor 1.

LIST OF REFERENCE NUMERALS

-   -   1 Refrigerant compressor    -   2 Drive unit    -   3 Piston/cylinder unit    -   4 Sound-damping unit    -   5 Metallic layer    -   6 Suction muffler    -   7 Discharge muffler    -   8 Compressor housing    -   9 Damping chamber of the suction muffler    -   10 Damping chamber of the discharge muffler    -   11 Functional surface

1. A refrigerant compressor comprising an electrical drive unit, apiston/cylinder unit which can be driven by the drive unit for thecyclical compression of refrigerant, and at least one sound-damping unitmade of a thermoplastic, through which sound-damping unit refrigerantcan flow and which sound-damping unit comprises at least one dampingchamber, wherein the at least one sound-damping unit is connected to thepiston/cylinder unit in order to enable an exchange of refrigerantbetween the sound-damping unit and piston/cylinder unit, wherein the atleast one sound-damping unit comprises at least in sections a functionalsurface, wherein the functional surface is embodied such that anemissivity of a section of the sound-damping unit comprising thefunctional surface is less than 0.7, preferably less than 0.5,particularly preferably less than 0.1, wherein the at least onesound-damping unit or at least one of the sound-damping units isembodied as a discharge muffler arranged downstream of thepiston/cylinder unit in the direction of flow.
 2. The refrigerantcompressor according to claim 1, wherein the thermoplastic comprisesadditives, for example, aluminum and/or chromium.
 3. The refrigerantcompressor according to claim 1, wherein the functional surface isembodied as a metallic layer.
 4. The refrigerant compressor according toclaim 3, wherein the at least one sound-damping unit is completelycovered by the metallic layer.
 5. The refrigerant compressor accordingto claim 3, wherein the metallic layer contains chromium and/oraluminum.
 6. The refrigerant compressor according to claim 3, whereinthe metallic layer is embodied as a metallic film.
 7. The refrigerantcompressor according to claim 6, wherein the at least one sound-dampingunit can be obtained by back injection-molding the metallic film.
 8. Therefrigerant compressor according to claim 3, wherein the metallic layeris spread onto and/or painted onto and/or glued onto and/or galvanizedonto the at least one sound-damping unit.
 9. The refrigerant compressoraccording to claim 1, wherein the at least one sound-damping unit or oneof the sound-damping units is embodied as a suction muffler arrangedupstream of the piston/cylinder unit in the direction of flow.